1. Field of the Invention
The novel acid addition salts of the present invention possess the advantageous antitumor properties of the known free base compound and in addition have unexpectedly high water-solubility, thus allowing preparation of useful clinical dosage forms for intravenous administration.
2. Description of the Prior Art
The acridine derivative m-AMSA [4'-(9-acridinylamino)methanesulfon-m-anisidide] was reported by Cain, et al. in Europ. J. Cancer 10:539-549 (1974) to possess significant antitumor activity in animal tumor systems. Since then, this compound has been subjected to clinical evaluation with very promising initial results.
When an antitumor agent such as m-AMSA is employed for human clinical use, it is recognized that solubility of the agent is often the controlling factor in determining route of administration and dosage forms. For instance, a water-soluble substance can be generally administered intravenously whereas a water-insoluble material is limited to other forms of parenteral administration such as intramuscular and subcutaneous. A therapeutic agent having water-solubility also facilitates preparation of oral and non-intravenous parenteral dosage forms for human administration. Thus, it is decidedly advantageous if a therapeutic agent is water-soluble, particularly when one considers that the most direct route for achieving therapeutic blood levels of a drug within the human body is by intravenous administration.
The free base form of m-AMSA has very limited solubility in water and thus cannot be used as a dosage form for intravenous administration. Attempts have been made to prepare acid addition salts to overcome this solubility problem, but the reported monohydrochloride and monomethanesulfonate salts also proved insufficiently water-soluble for clinical use. The formulation presently in clinical use consists of two sterile liquids combined prior to use. A solution of m-AMSA in anhydrous N,N-dimethylacetamide is contained in an ampule. A separate vial contains an aqueous L(+) lactic acid solution for use as a diluent. When mixed the resulting m-AMSA solution is administered by i.v. infusion.
While the present clinical formulation provides an intravenous dosage form, it suffers from several disadvantages. In addition to the obvious difficulties in preparing and administering the dosage form, it contains dimethylacetamide as a vehicle. Dimethylacetamide has been reported to show various toxic symptoms in animals and may thus prove to be unacceptable or undesirable as a pharmaceutical vehicle.
It is accordingly an object of the present invention to provide a water-soluble, stable, therapeutically acceptable form of m-AMSA which can be administered intravenously (as well as by other routes) and which does not contain or require dimethylacetamide as a pharmaceutical vehicle. This object as well as other features and advantages of the invention will be readily apparent to those skilled in the art from the disclosure set out below.